U.S. patent application number 13/192215 was filed with the patent office on 2013-01-31 for apparatus and methods for delivery of a functional material to an image forming member.
This patent application is currently assigned to XEROX CORPORATION. The applicant listed for this patent is Nan-Xing Hu, Richard A. Klenkler, Yu Liu, Vladislav Skorokhod, Sarah J. Vella. Invention is credited to Nan-Xing Hu, Richard A. Klenkler, Yu Liu, Vladislav Skorokhod, Sarah J. Vella.
Application Number | 20130028636 13/192215 |
Document ID | / |
Family ID | 47597316 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130028636 |
Kind Code |
A1 |
Hu; Nan-Xing ; et
al. |
January 31, 2013 |
APPARATUS AND METHODS FOR DELIVERY OF A FUNCTIONAL MATERIAL TO AN
IMAGE FORMING MEMBER
Abstract
The presently disclosed embodiments relate generally to an image
forming apparatus comprising: a) an imaging member, b) a bias
charging roller in contact with the surface of the imaging member,
and c) a delivery unit in contact with the surface of the bias
charge roller, wherein the delivery unit is fabricated as a polymer
matrix impregnated with functional materials, such that the
functional material is transferred onto the imaging member from the
delivery unit via the bias charging roller. Embodiments also
pertain to an improved electrophotographic imaging member
comprising a very thin outer layer on the imaging member surface,
where the outer layer comprises functional materials, such as
paraffin, that act as a lubricant and or a barrier against moisture
and/or surface contaminants. The improved imaging member exhibits
improved xerographic performance, such as reduced friction and
deletions in high humidity conditions.
Inventors: |
Hu; Nan-Xing; (Oakville,
CA) ; Liu; Yu; (Mississauga, CA) ; Vella;
Sarah J.; (Windsor, CA) ; Klenkler; Richard A.;
(Oakville, CA) ; Skorokhod; Vladislav;
(Mississauga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hu; Nan-Xing
Liu; Yu
Vella; Sarah J.
Klenkler; Richard A.
Skorokhod; Vladislav |
Oakville
Mississauga
Windsor
Oakville
Mississauga |
|
CA
CA
CA
CA
CA |
|
|
Assignee: |
XEROX CORPORATION
Norwalk
CT
|
Family ID: |
47597316 |
Appl. No.: |
13/192215 |
Filed: |
July 27, 2011 |
Current U.S.
Class: |
399/159 ;
399/176 |
Current CPC
Class: |
G03G 15/0208 20130101;
G03G 21/0094 20130101 |
Class at
Publication: |
399/159 ;
399/176 |
International
Class: |
G03G 15/00 20060101
G03G015/00; G03G 15/02 20060101 G03G015/02 |
Claims
1. An image forming apparatus comprising: a) an imaging member
having a charge retentive-surface for developing an electrostatic
latent image thereon, wherein the imaging member comprises: an
optional support substrate, and one or more photoconductive layers
disposed on the substrate; b) a charging unit comprising a charging
roller disposed in contact with the surface of the imaging member;
and c) a delivery unit disposed in contact with the surface of the
charging roller, wherein the delivery unit applies a layer of
functional material to the surface of the charging roller and the
charging roller in turn applies a layer of the functional material
onto the surface of the imaging member.
2. The image forming apparatus of claim 1, wherein the delivery
unit comprises a supplying unit containing one or more functional
materials.
3. The image forming apparatus of claim 2, wherein the supplying
unit is selected from the group consisting of reservoir, polymeric
matrix, porous foam, membrane, and fabrics.
4. The image forming apparatus of claim 1, wherein the delivery
unit comprises a delivery member comprising; a support member, and
an elastomeric layer disposed on the support member, wherein the
elastomeric layer is comprised of a polymer matrix containing one
or more functional materials dispersed within the polymer
matrix.
5. The image forming apparatus of claim 4, wherein the polymer
matrix comprises a cross-linked polymer selected from the group
consisting of silicones, polyurethanes, polyesters,
fluoro-silicones, polyolefin, fluoroelastomers, synthetic rubber,
natural rubber, and mixtures thereof.
6. The image forming apparatus of claim 4, wherein the elastomeric
layer comprises a cross-linked silicone polymer.
7. The image forming apparatus of claim 4, wherein the support
member comprises a material selected from the group consisting of a
metal, plastics, ceramic, and mixtures thereof.
8. The image forming apparatus of claim 4, wherein the amount of
the functional material delivered onto the surface of the imaging
member is controlled by the diffusion rate of the functional
material in the elastic material.
9. The image forming apparatus of claim 1, wherein the functional
material comprises a liquid material selected from the group
consisting of a lubricant material, a hydrophobic material, an
oleophobic material, an amphiphilic material, and mixtures
thereof.
10. The image forming apparatus of claim 1, wherein the functional
material comprises a liquid material selected from the group
consisting of hydrocarbons, fluorocarbons, mineral oil, synthetic
oil, natural oil, and mixtures thereof.
11. The image forming apparatus of claim 1, wherein the functional
material comprises paraffin oil.
12. The image forming apparatus of claim 1, wherein the functional
material is present on the surface of the imaging member in an
amount of from about 0.5 nanogram/cm.sup.2 to about 500
nanograms/cm.sup.2.
13. The image forming apparatus of claim 4, wherein the delivery
member has a smooth surface or a patterned surface pattern.
14. The image forming apparatus of claim 13, wherein the patterned
surface comprises indentations or protrusions that have a shape
selected from the group consisting of circles, rods, ovals,
squares, triangles, polygons, and mixtures thereof,
15. An image forming system comprising: a) an electrophotographic
photoconductive member; b) a charging unit comprising a charging
roller disposed in contact with the surface of the
electrophotographic photoconductive member, which is capable of
charging the photoconductive member to a predetermined electric
potential; c) a delivery member disposed in contact with the
surface of the charging roller to apply a layer of functional
material onto the surface of the charging roller that in turn
applies a layer of the functional material to the surface of the
photoconductive member; d) an electrostatic latent image forming
unit that develop an electrostatic latent image on the
photoreceptor member; d) a toner developer unit for applying toner
to the photoconductive member to develop a toner image on the
photoconductive member; e) a transfer unit for transferring the
developed toner image from the photoconductive member to a copy
substrate or an intermediate member; and a cleaning unit for
cleaning the photoconductive member to remove remaining toner
particles.
16. The image forming system of claim 15, wherein the delivery
member is a roller comprising: a support member, and an elastomeric
layer disposed on the support member, wherein the elastomeric layer
is comprised of a polymer matrix containing one or more functional
materials dispersed within the polymer matrix,
17. The image forming system of claim 16, wherein the elastomeric
layer comprises a cross-linked silicone polymer and a paraffin
compound dispersed within the polymer.
18. The image forming system of claim 15, wherein the amount of the
functional material delivered onto the surface of the imaging
member is controlled by the diffusion rate of the functional
material in the elastic material.
19. A method for delivering a functional material onto a surface of
an imaging member comprising: providing the image forming apparatus
of claim 1; applying the functional material onto the surface of
the charging unit through the delivery member; and applying the
functional material onto the surface of the imaging member through
the charging unit to form an outer layer of the functional material
on the surface of the imaging member.
20. The method of claim 19, wherein the surface of the delivery
member has a surface pattern and the step of applying the
hydrophobic functional material onto the surface of the imaging
member through the charging unit forms an outer layer of the
hydrophobic functional material on the surface of the imaging
member having the surface pattern.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Reference is made to commonly owned and co-pending, U.S.
patent application Ser. No. ______ (not yet available) to Vella et
al., filed the same day as the present application, entitled,
"Composition for Use in an Apparatus for Delivery of a Functional
Material to an Image Forming Member (Attorney Docket No.
20110391-396040), the entire disclosure of which are incorporated
herein by reference in its entirety.
BACKGROUND
[0002] The presently disclosed embodiments relate generally to
layers that are useful in imaging apparatus members and components,
for use in electrophotographic, including digital printing,
apparatuses. More particularly, the embodiments pertain to an
improved electrophotographic imaging member comprising a very thin
outer layer on the imaging member surface, where the outer layer
comprises functional materials that act as a lubricant and or a
barrier against moisture and/or surface contaminants to address
high torque and image quality such as A-zone deletion. The very
thin outer layer is applied to the imaging member on a nano-scale
or molecular level. The improved imaging member exhibits improved
xerographic performance, such as improved interaction with blade
cleaner and reduced image deletions in high humidity conditions.
The embodiments also pertain to methods and systems for delivering
the functional materials to the surface of the imaging member.
[0003] In electrophotography or electrophotographic printing, the
charge retentive surface, typically known as a photoreceptor, is
electrostatically charged, and then exposed to a light pattern of
an original image to selectively discharge the surface in
accordance therewith. The resulting pattern of charged and
discharged areas on the photoreceptor form an electrostatic charge
pattern, known as a latent image, conforming to the original image.
The latent image is developed by contacting it with a finely
divided electrostatically attractable powder known as toner. Toner
is held on the image areas by the electrostatic charge on the
photoreceptor surface. Thus, a toner image is produced in
conformity with a light image of the original being reproduced or
printed. The toner image may then be transferred to a substrate or
support member (e.g., paper) directly or through the use of an
intermediate transfer member, and the image affixed thereto to form
a permanent record of the image to be reproduced or printed.
Subsequent to development, excess toner left on the charge
retentive surface is cleaned from the surface. The process is
useful for light lens copying from an original or printing
electronically generated or stored originals such as with a raster
output scanner (ROS), where a charged surface may be imagewise
discharged in a variety of ways.
[0004] The described electrophotographic copying process is well
known and is commonly used for light lens copying of an original
document. Analogous processes also exist in other
electrophotographic printing applications such as, for example,
digital laser printing and reproduction where charge is deposited
on a charge retentive surface in response to electronically
generated or stored images.
[0005] To charge the surface of a photoreceptor, a contact type
charging device has been used, such as disclosed in U.S. Pat. No.
4,387,980 and U.S. Pat. No. 7,580,655, which are incorporated
herein by reference. The contact type charging device, also termed
"bias charge roll" (BCR) includes a conductive member which is
supplied a voltage from a power source with a D.C. voltage
superimposed with an A.C. voltage of no less than twice the level
of the D.C. voltage. The charging device contacts the image bearing
member (photoreceptor) surface, which is a member to be charged.
The outer surface of the image bearing member is charged at the
contact area. The contact type charging device charges the image
bearing member to a predetermined potential.
[0006] Electrophotographic photoreceptors can be provided in a
number of forms. For example, the photoreceptors can be a
homogeneous layer of a single material, such as vitreous selenium,
or it can be a composite layer containing a photoconductive layer
and another material. In addition, the photoreceptor can be
layered. Multilayered photoreceptors or imaging members have at
least two layers, and may include a substrate, a conductive layer,
an optional undercoat layer (sometimes referred to as a "charge
blocking layer" or "hole blocking layer"), an optional adhesive
layer, a photogenerating layer (sometimes referred to as a "charge
generation layer," "charge generating layer," or "charge generator
layer"), a charge transport layer, and an optional overcoating
layer in either a flexible belt form or a rigid drum configuration.
In the multilayer configuration, the active layers of the
photoreceptor are the charge generation layer (CGL) and the charge
transport layer (CTL). Enhancement of charge transport across these
layers provides better photoreceptor performance. Multilayered
flexible photoreceptor members may include an anti-curl layer on
the backside of the substrate, opposite to the side of the
electrically active layers, to render the desired photoreceptor
flatness.
[0007] Conventional photoreceptors are disclosed in the following
patents, a number of which describe the presence of light
scattering particles in the undercoat layers: Yu, U.S. Pat. No.
5,660,961; Yu, U.S. Pat. No. 5,215,839; and Katayama et al., U.S.
Pat. No. 5,958,638. The term "photoreceptor" or "photoconductor" is
generally used interchangeably with the terms "imaging member." The
term "electrophotographic" includes "electrophotographic" and
"xerographic." The terms "charge transport molecule" are generally
used interchangeably with the terms "hole transport molecule."
[0008] To further increase the service life of the photoreceptor,
use of overcoat layers has also been implemented to protect
photoreceptors and improve performance, such as wear resistance.
However, these low wear overcoats are associated with poor image,
quality due to A-zone deletion in a humid environment as the wear
rates decrease to a certain level. In addition, high torque
associated with low wear overcoats in A-zone also causes severe
issues with BCR charging systems, such as motor failure and blade
damage. As a result, use of a low wear overcoat with BCR charging
systems is still a challenge, and there is a need to find a way to
achieve the life target with overcoat technology in such
systems.
SUMMARY
[0009] According to aspects illustrated herein, there is provided
an image forming apparatus comprising: a) an imaging member having
a charge retentive-surface for developing an electrostatic latent
image thereon, wherein the imaging member comprises: an optional
support substrate, and one or more photoconductive layers disposed
on the substrate; b) a charging unit comprising a charging roller
disposed in contact with the surface of the imaging member; and c)
a delivery unit disposed in contact with the surface of the
charging roller, wherein the delivery unit applies a layer of
functional material to the surface of the charging roller and the
charging roller in turn applies a layer of the functional material
onto the surface of the imaging member. The delivery unit
comprises, in embodiments, a delivery member comprising support
member, and an elastomeric layer disposed on the support member,
wherein the elastomeric layer is comprised of a polymer matrix
containing one or more functional materials dispersed within the
polymer matrix.
[0010] In another embodiment, there is provided an image forming
system comprising: a) an electrophotographic photoconductive
member; b) a charging unit comprising a charging roller disposed in
contact with the surface of the electrophotographic photoconductive
member, which is capable of charging the photoconductive member to
a predetermined electric potential; c) a delivery member disposed
in contact with the surface of the charging roller to apply a layer
of functional material onto the surface of the charging roller that
in turn applies a layer of the functional material to the surface
of the photoconductive member; d) an electrostatic latent image
forming unit that develop an electrostatic latent image on the
photoreceptor member; d) a toner developer unit for applying toner
to the photoconductive member to develop a toner image on the
photoconductive member; e) a transfer unit for transferring the
developed toner image from the photoconductive member to a copy
substrate or an intermediate member; and f) a cleaning unit for
cleaning the photoconductive member to remove remaining toner
particles.
[0011] In yet further embodiments, there is provided a method for
delivering a functional material onto a surface of an imaging
member comprising: providing the image forming apparatus as
described above; applying the functional material onto the surface
of the charging unit through the delivery member; and applying the
functional material onto the surface of the imaging member through
the charging unit to form an outer layer of the functional material
on the surface of the imaging member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a better understanding, reference may be made to the
accompanying figures.
[0013] FIG. 1 is a cross-sectional view of an imaging member in a
drum configuration according to the present embodiments;
[0014] FIG. 2 is a cross-sectional view of an imaging member in a
belt configuration according to the present embodiments;
[0015] FIG. 3 is a cross-sectional view of a system implementing a
delivery member in a customer replaceable unit (CRU) according to
the present embodiments;
[0016] FIG. 4 is a side cross-sectional view of a delivery member
for making an outer layer of an imaging member according to the
present embodiments;
[0017] FIG. 5 illustrates a test image-forming apparatus according
to the present embodiments; and
[0018] FIG. 6 is a print test demonstrating A-zone deletion results
of prints made with the system according to the present embodiments
as compared to those made with a control system (without use of
delivery member with hydrophobic functional materials).
DETAILED DESCRIPTION
[0019] In the following description, reference is made to the
accompanying drawings, which form a part hereof and which
illustrate several embodiments. It is understood that other
embodiments may be used and structural and operational changes may
be made without departure from the scope of the present
disclosure.
[0020] The disclosed embodiments are directed generally to an
improved electrophotographic imaging member comprising a very thin
outer layer on the imaging member surface that comprises functional
materials that act as a lubricant and or a barrier against moisture
and/or surface contaminants. The outer layer imparts improved
xerographic performance to imaging members incorporating such an
outer layer, such as improved wear resistance, low friction, and
reduced image defects due to deletion in high humidity
conditions.
[0021] The embodiments also pertain to methods for making the
improved electrophotographic imaging member through delivering the
functional materials to the outer layer of an imaging surface. As
used herein, "functional material" is a material that provides
maintenance of desired photoreceptor function. For example, the
functional material may be one that is continuously applied onto
the photoreceptor surface through direct contact transfer and which
can maintain the desired function(s) of the photoreceptor by
providing continued lubrication and surface protection. Lubrication
of the photoreceptor surface improves interaction with other
components in a xerographic system, such as for example, the blade
cleaner to reduce torque and blade damage. By maintaining a thin
layer of surface material on the photoreceptor, the functional
material also provides surface protection to prevent image deletion
in, for example, a humid environment such as A-zone.
[0022] In the present embodiments, there is provided an image
forming apparatus comprising: a) an imaging member having a charge
retentive-surface for developing an electrostatic latent image
thereon; b) a charging unit comprising a charging roller disposed
in contact with the surface of the imaging member; and c) a
delivery unit disposed in contact with the surface of the charging
roller, wherein the delivery unit applies a layer of functional
material to the surface of the charging roller and the charging
roller in turn applies a layer of the functional material onto the
surface of the imaging member. In specific embodiments, the
delivery unit comprises a delivery roll implemented in the imaging
forming apparatus, such as a customer replaceable unit (CRU) of a
xerographic printing system, such that the delivery roll delivers
functional materials to the outer layer, for example, an overcoat
layer, of an imaging member or photoreceptor. The exemplary
embodiments of this disclosure are described below with reference
to the drawings. The specific terms are used in the following
description for clarity, selected for illustration in the drawings
and not to define or limit the scope of the disclosure. The same
reference numerals are used to identify the same structure in
different figures unless specified otherwise. The structures in the
figures are not drawn according to their relative proportions and
the drawings should not be interpreted as limiting the disclosure
in size, relative size, or location. In addition, though the
discussion will address negatively charged systems, the imaging
members of the present disclosure may also be used in positively
charged systems.
[0023] FIG. 1 is an exemplary embodiment of a multilayered
electrophotographic imaging member or photoreceptor having a drum
configuration. The substrate may further be in a cylinder
configuration. As can be seen, the exemplary imaging member
includes a rigid support substrate 10, an electrically conductive
ground plane 12, an undercoat layer 14, a charge generation layer
18 and a charge transport layer 20. An optional overcoat layer 32
disposed on the charge transport layer may also be included. The
rigid substrate may be comprised of a material selected from the
group consisting of a metal, metal alloy, aluminum, zirconium,
niobium, tantalum, vanadium, hafnium, titanium, nickel, stainless
steel, chromium, tungsten, molybdenum, and mixtures thereof. The
substrate may also comprise a material selected from the group
consisting of a metal, a polymer, a glass, a ceramic, and wood.
[0024] The charge generation layer 18 and the charge transport
layer 20 forms an imaging layer described here as two separate
layers. In an alternative to what is shown in the figure, the
charge generation layer may also be disposed on top of the charge
transport layer. It will be appreciated that the functional
components of these layers may alternatively be combined into a
single layer.
[0025] FIG. 2 shows an imaging member or photoreceptor having a
belt configuration according to the embodiments. As shown, the belt
configuration is provided with an anti-curl back coating 1, a
supporting substrate 10, an electrically conductive ground plane
12, an undercoat layer 14, an adhesive layer 16, a charge
generation layer 18, and a charge transport layer 20. An optional
overcoat layer 32 and ground strip 19 may also be included. An
exemplary photoreceptor having a belt configuration is disclosed in
U.S. Pat. No. 5,069,993, which is hereby incorporated by
reference.
[0026] As discussed above, an electrophotographic imaging member
generally comprises at least a substrate layer, an imaging layer
disposed on the substrate and an optional overcoat layer disposed
on the imaging layer. In further embodiments, the imaging layer
comprises a charge generation layer disposed on the substrate and
the charge transport layer disposed on the charge generation layer.
In other embodiments, an undercoat layer may be included and is
generally located between the substrate and the imaging layer,
although additional layers may be present and located between these
layers. The imaging member may also include an anti-curl back
coating layer in certain embodiments. The imaging member can be
employed in the imaging process of electrophotography, where the
surface of an electrophotographic plate, drum, belt or the like
(imaging member or photoreceptor) containing a photoconductive
insulating layer on a conductive layer is first uniformly
electrostatically charged. The imaging member is then exposed to a
pattern of activating electromagnetic radiation, such as light. The
radiation selectively dissipates the charge on the illuminated
areas of the photoconductive insulating layer while leaving behind
an electrostatic latent image. This electrostatic latent image may
then be developed to form a visible image by depositing charged
particles of same or opposite polarity on the surface of the
photoconductive insulating layer. The resulting visible image may
then be transferred from the imaging member directly or indirectly
(such as by a transfer or other member) to a print substrate, such
as transparency or paper. The imaging process may be repeated many
times with reusable imaging members.
[0027] Common print quality issues are strongly dependent on the
quality and interaction of these photoreceptor layers. For example,
when a photoreceptor is used in combination with a contact charger
and a toner obtained by chemical polymerization (polymerization
toner), image quality may be deteriorated due to a surface of the
photoreceptor being stained with a discharge product produced in
contact charging or the polymerization toner remaining after a
cleaning step. Still further, repetitive cycling causes the
outermost layer of the photoreceptor to experience a high degree of
frictional contact with other machine subsystem components used to
clean and/or prepare the photoreceptor for imaging during each
cycle. When repeatedly subjected to cyclic mechanical interactions
against the machine subsystem components, a photoreceptor can
experience severe frictional wear at the outermost organic
photoreceptor layer surface that can greatly reduce the useful life
of the photoreceptor. Ultimately, the resulting wear impairs
photoreceptor performance and thus image quality. Another type of
common image defect is thought to result from the accumulation of
charge somewhere in the photoreceptor. Consequently, when a
sequential image is printed, the accumulated charge results in
image density changes in the current printed image that reveals the
previously printed image. In the xerographic process spatially
varying amounts of positive charges from the transfer station find
themselves on the photoreceptor surface. If this variation is large
enough it will manifest itself as a variation in the image
potential in the following xerographic cycle and print out as a
defect.
[0028] A conventional approach to photoreceptor life extension is
to apply an overcoat layer with wear resistance. For bias charge
roller (BCR) charging systems, overcoat layers are associated with
a trade-off between A-zone deletion (i.e. an image defect occurred
in A-zone: 28.degree. C., 85% RH) and photoreceptor wear rate. For
example, most organic photoconductor (OPC) materials sets require a
certain level of wear rate in order to suppress A-zone deletion,
thus limiting the life of a photoreceptor. The present embodiments,
however, have demonstrated a decrease in wear rate of a
photoreceptor while maintaining the image quality of the
photoreceptor, such as decreased image deletions. The present
embodiments provide photoreceptor technology for BCR charging
systems with a significantly expanded life.
[0029] The present embodiments employ delivery units to deliver an
ultra thin layer of functional materials onto the photoreceptor
surface through a charging roller. The functional materials applied
to the photoreceptor surface act as lubricant and or a barrier
against moisture and surface contaminants and improve xerographic
performance in high humidity conditions, such as for example,
A-zone environment. The ultra thin layer may be provided on a
nano-scale or molecular level.
[0030] In embodiments, there is provided a method for controlled
delivery of functional materials onto the surface of a
photoreceptor by continuous delivery of the functional material to
provide an ultra thin layer of barrier against moisture and surface
contaminants and improve xerographic performance in high humidity
conditions (A-zone: 28.degree. C., 85% RH). From prior mechanistic
studies, it has been demonstrated that A-zone deletion is caused by
a number of occurrences, including, high energy charging which
results in the formation of hydrophilic chemical species (e.g.,
--OH, --COOH) on the photoreceptor surface, water being physically
absorbed on the hydrophilic photoreceptor surface in humid
environment, and an increase in the surface conductivity of the
photoreceptor due to the absorbed water layer and toner
contaminants. Thus, to address these issues, the present
embodiments disclose a controlled delivery of an ultra thin layer
of functional materials such as hydrophobic material that can be
applied directly to the photoreceptor surface continuously and is
capable of preventing A-zone deletion for low wear
photoreceptors.
[0031] In embodiments, a functional material is continuously
delivered on the photoreceptor to form an ultra thin layer of
lubricant to protect machine subsystem components, through reducing
friction between the cleaning blade and the photoreceptor surface
or at the contact interface between the photoreceptor surface and
other relevant components. This lubricant further reduces the
resultant torque and vibration so that the actuator and involved
transmission mechanisms can move the photoreceptor or other
relevant components in a smoother way. Therefore, the lubricant
improves the printed image quality, which may be deteriorated due
to aforementioned reasons, and further protects these components
and extends their service life.
[0032] In embodiments, there is provided an image forming apparatus
for delivering functional materials onto photoreceptor. The
apparatus typically comprises an imaging member; a charging unit
comprising a charging roller disposed in contact with the surface
of the imaging member; and a delivery unit disposed in contact with
the surface of the charging roller, wherein the delivery unit
applies a layer of functional material to the surface of the
charging roller and the charging roller in turn applies a layer of
the functional material onto the surface of the imaging member. The
delivery unit may comprise a supplying unit containing one or more
functional materials to directly provide the functional materials
to the charging roller. For instance, the functional materials by
the supplying unit may be stored in and delivered by a reservoir,
polymeric matrix, porous foam, membrane, fabrics or the likes. In
further embodiments, the delivery unit comprises a delivery member
such as a delivery roll for providing the functional materials to
the charging roller, which in return deliver the functional
materials onto the surface of the imaging member.
[0033] FIGS. 3 and 4 illustrate delivery members according to the
present embodiments. In FIG. 3, there is illustrated an
image-forming apparatus comprising a photoreceptor 34, a BCR 36 and
a delivery member 38. The delivery member 38 contacts the BCR 36 to
deliver an ultra thin layer of the functional material onto the
surface of the BCR 36. The BCR 36, in turn, transfers the
functional material onto the surface of the photoreceptor 34. The
delivery member may be integrated into a xerographic printing
system in various configurations and positions. As can be seen, as
the overcoated photoreceptor drum 34 rotates, the delivery member
38 impregnated with the functional material delivers the functional
materials to the surface of the BCR roller 36, which in turn,
delivers the functional materials to the surface of the overcoated
photoreceptor 34 through contact diffusion. For example, the amount
of the functional material delivered onto the surface of the
imaging member is controlled by the diffusion rate of the
functional material in the elastic material of the delivery member.
Subsequently, the photoreceptor 34 is substantially uniformly
charged by the BCR 36 to initiate the electrophotographic
reproduction process. The charged photoreceptor is then exposed to
a light image to create an electrostatic latent image on the
photoreceptive member (not shown). This latent image is
subsequently developed into a visible image by a toner developer
40. Thereafter, the developed toner image is transferred from the
photoreceptive member to a copy sheet or some other image support
substrate to which the image may be permanently affixed for
producing a reproduction of the original document (not shown). The
photoreceptor surface is generally then cleaned with a cleaner 42
to remove any residual developing material therefrom, in
preparation for successive imaging cycles. While not necessary, a
supplying unit containing the functional materials may be included
for supply of the functional material to the delivery member. In
embodiments that do have the supplying unit, the supplying unit may
be selected from the group consisting of reservoir, polymeric
matrix, porous foam, membrane, and fabrics.
[0034] FIG. 4 illustrates the delivery member 38 according to the
present embodiments, and a cross-section thereof. The delivery
member 38 comprises an elastomeric matrix 44 disposed around a
support member 46. In embodiments, the support member 46 is a
stainless steel rod. The support member can further comprise a
material selected from the group consisting of a metal, plastics,
ceramic, and mixtures thereof. The diameter of the support member
and the thickness of the elastomeric matrix may be varied depending
on the application needs. In specific embodiments, the support
member has a diameter of, for example, from about 3 mm to about 10
mm. In specific embodiments, the elastomeric matrix has a thickness
of, for example, from about 20 .mu.m to about 20 mm. In
embodiments, the elastomeric matrix 44 may comprise hydrophobic
functional materials 48 retained within a polymer matrix 50 such as
a cross-linked silicone which forms a matrix that facilitates
retainment of the functional materials.
[0035] In the present embodiments, the functional material is
integrated into the composition of the delivery member 38 and thus
eliminates the need for a separate supply of materials within the
system or the need to constantly reapplying the materials to the
deliver member. Thus, the delivery member 36 serves the dual
purpose of a reservoir and distributor of the functional material.
In addition, the delivery members fabricated according to the
present embodiments have shown to contain sufficient quantities of
the functional material to continuously supply an ultra thin layer
of the functional material to the surface of the
BCR/photoreceptor.
[0036] In embodiments, the functional material can be an organic or
inorganic compound, oligomer or polymer, or a mixture thereof. The
functional materials may be in the form of liquid, wax, or gel, and
a mixture thereof. The functional material may also be selected
from the group consisting of a lubricant material, a hydrophobic
material, an oleophobic material, an amphiphilic material, and
mixtures thereof. Illustrative examples of functional materials may
include, for example, a liquid material selected from the group
consisting of hydrocarbons, fluorocarbons, mineral oil, synthetic
oil, natural oil, and mixtures thereof. The functional materials
may further contain a functional group that facilitates adsorption
of the functional materials on the photoreceptor surface, and
optionally a reactive group that can chemically modify the
photoreceptor surface. For examples, the functional materials may
comprise paraffinic compound, alkyl alkoxy-silanes, or the mixture
thereof. In embodiments, the polymer matrix be comprised of a
polymer selected from the group consisting of silicones,
polyurethanes, polyesters, fluoro-silicones, polyolefin,
fluoroelastomers, synthetic rubber, natural rubber, and mixtures
thereof.
[0037] In a specific embodiment, the elastomeric matrix 44 is
composed of paraffin-impregnated silicone cast around the support
member 46. The paraffin-impregnated silicone is prepared by mixing
paraffin into a cross-linkable polydimethylsiloxane (PDMS) and then
casting the mixture onto the support member 46 by use of a mold.
Thereafter, the elastomeric matrix 44 is cured. After curing, the
PDMS coated rod is extracted from the mold and may be further
impregnated by immersion in a functional material, such as
paraffin. In embodiments, the liquid cross-linkable PDMS is
prepared from a two-component system, namely, a base agent and a
curing agent. In further embodiments, the base agent and curing
agent are present in a weight ratio of from about 50:1 to 2:1, or
from about 20:1 to about 5:1. In embodiments, the functional
material can be incorporated into the polymer matrix at a weight
ratio of up to about 1:1, or from about 1:10 to about 1:2
[0038] The delivery member may be presented in a roll or have other
configurations such as a web. The thickness of elastic materials
may be varied, for example, from about 20 .mu.m to about 20 mm, or
from about 50 .mu.m to about 10 mm. The delivery member may have a
surface pattern comprising indentations or protrusions that have a
shape selected from the group consisting of circles, rods, ovals,
squares, triangles, polygons, and mixtures thereof.
[0039] In further embodiments, the functional material is delivered
to the surface of a photoreceptor from the delivery member by
contacting an elastic outer layer of the delivery member
impregnated with the functional material to the surface of the
charging roller, which in return delivers the functional materials
to the surface of the photoreceptor. The diffusion rate of the
functional material in the matrix of the elastic composition of the
delivery member helps control the delivery rate of the functional
material. Consequently, the delivery material forms an outer layer
on a nano-scale or molecular level, providing both an economical
method and avoiding contamination from excess functional materials
on the photoreceptor and charging member. In embodiments, the
functional material may be applied directly to the imaging layer in
place of the overcoat layer.
[0040] In embodiments, the amount of functional material delivered
onto the photoreceptor surface should be sufficient to retain the
photoreceptor performance properties. The functional material can
be present on the photoreceptor surface at various amount, for
example, at a molecular level, or amount of from about 0.5
nanogram/cm.sup.2 to about 500 nanograms/cm.sup.2, or from about 1
nanogram/cm.sup.2 to about 100 nanogram/cm.sup.2. The present
embodiments provide a photoreceptor that exhibits both reduced wear
rate and reduced ghosting as compared to a photoreceptor without
the outer layer.
[0041] The Overcoat Layer
[0042] Other layers of the imaging member may include, for example,
an optional over coat layer 32. An optional overcoat layer 32, if
desired, may be disposed over the charge transport layer 20 to
provide imaging member surface protection as well as improve
resistance to abrasion. In embodiments, the overcoat layer 32 may
have a thickness ranging from about 0.1 micrometer to about 15
micrometers or from about 1 micrometer to about 10 micrometers, or
in a specific embodiment, about 3 micrometers to about 10
micrometers. These overcoating layers typically comprise a charge
transport component and an optional organic polymer or inorganic
polymer. These overcoating layers may include thermoplastic organic
polymers or cross-linked polymers such as thermosetting resins, UV
or e-beam cured resins, and the likes. The overcoat layers may
further include a particulate additive such as metal oxides
including aluminum oxide and silica, or low surface energy
polytetrafluoroethylene (PTFE), and combinations thereof.
[0043] Any known or new overcoat materials may be included for the
present embodiments. In embodiments, the overcoat layer may include
a charge transport component or a cross-linked charge transport
component. In particular embodiments, for example, the overcoat
layer comprises a charge transport component comprised of a
tertiary arylamine containing substituent capable of self
cross-linking or reacting with the polymer resin to form a cured
composition. Specific examples of charge transport component
suitable for overcoat layer comprise the tertiary arylamine with a
general formula of
##STR00001##
wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 each
independently represents an aryl group having about 6 to about 30
carbon atoms, Ar.sup.5 represents aromatic hydrocarbon group having
about 6 to about 30 carbon atoms, and k represents 0 or 1, and
wherein at least one of Ar.sup.1, Ar.sup.2, Ar.sup.3 Ar.sup.4, and
Ar.sup.5 comprises a substituent selected from the group consisting
of hydroxyl (--OH), a hydroxymethyl (--CH.sub.2OH), an alkoxymethyl
(--CH.sub.2OR, wherein R is an alkyl having 1 to about 10 carbons),
a hydroxylalkyl having 1 to about 10 carbons, and mixtures thereof.
In other embodiments, Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4
each independently represent a phenyl or a substituted phenyl
group, and Ar.sup.5 represents a biphenyl or a terphenyl group.
[0044] Additional examples of charge transport component which
comprise a tertiary arylamine include the following:
##STR00002## ##STR00003##
and the like, wherein R is a substituent selected from the group
consisting of hydrogen atom, and an alkyl having from 1 to about 6
carbons, and m and n each independently represents 0 or 1, wherein
m+n>1, in specific embodiments, the overcoat layer may include
an additional curing agent to form a cured, crosslinked overcoat
composition. Illustrative examples of the curing agent may be
selected from the group consisting of a melamine-formaldehyde
resin, a phenol resin, an isocyalate or a masking isocyalate
compound, an acrylate resin, a polyol resin, or mixtures thereof.
In embodiments, the crosslinked overcoat composition has an average
modulus ranging from about 3 GPa to about 5 GPa, as measured by
nano-indentation method using, for example, nanomechanical test
instruments manufactured by Hysitron Inc. (Minneapolis, Minn.).
[0045] The Substrate
[0046] The photoreceptor support substrate 10 may be opaque or
substantially transparent, and may comprise any suitable organic or
inorganic material having the requisite mechanical properties. The
entire substrate can comprise the same material as that in the
electrically conductive surface, or the electrically conductive
surface can be merely a coating on the substrate. Any suitable
electrically conductive material can be employed, such as for
example, metal or metal alloy. Electrically conductive materials
include copper, brass, nickel, zinc, chromium, stainless steel,
conductive plastics and rubbers, aluminum, semitransparent
aluminum, steel, cadmium, silver, gold, zirconium, niobium,
tantalum, vanadium, hafnium, titanium, nickel, niobium, stainless
steel, chromium, tungsten, molybdenum, paper rendered conductive by
the inclusion of a suitable material therein or through
conditioning in a humid atmosphere to ensure the presence of
sufficient water content to render the material conductive, indium,
tin, metal oxides, including tin oxide and indium tin oxide, and
the like. It could be single metallic compound or dual layers of
different metals and/ or oxides.
[0047] The substrate 10 can also be formulated entirely of an
electrically conductive material, or it can be an insulating
material including inorganic or organic polymeric materials, such
as MYLAR, a commercially available biaxially oriented polyethylene
terephthalate from DuPont, or polyethylene naphthalate available as
KALEDEX 2000, with a ground plane layer 12 comprising a conductive
titanium or titanium/zirconium coating, otherwise a layer of an
organic or inorganic material having a semiconductive surface
layer, such as indium tin oxide, aluminum, titanium, and the like,
or exclusively be made up of a conductive material such as,
aluminum, chromium, nickel, brass, other metals and the like. The
thickness of the support substrate depends on numerous factors,
including mechanical performance and economic considerations.
[0048] The substrate 10 may have a number of many different
configurations, such as for example, a plate, a cylinder, a drum, a
scroll, an endless flexible belt, and the like. In the case of the
substrate being in the form of a belt, as shown in FIG. 2, the belt
can be seamed or seamless. In embodiments, the photoreceptor herein
is in a drum configuration.
[0049] The thickness of the substrate 10 depends on numerous
factors, including flexibility, mechanical performance, and
economic considerations. The thickness of the support substrate 10
of the present embodiments may be at least about 500 micrometers,
or no more than about 3,000 micrometers, or be at least about 750
micrometers, or no more than about 2500 micrometers.
[0050] An exemplary substrate support 10 is not soluble in any of
the solvents used in each coating layer solution, is optically
transparent or semi-transparent, and is thermally stable up to a
high temperature of about 150.degree. C. A substrate support 10
used for imaging member fabrication may have a thermal contraction
coefficient ranging from about 1.times.10.sup.-5 per .degree. C. to
about 3.times.10.sup.-5 per .degree. C. and a Young's Modulus of
between about 5.times.10.sup.-5 psi (3.5.times.10.sup.-4
Kg/cm.sup.2) and about 7.times.10.sup.-5 psi (4.9.times.10.sup.-4
Kg/cm.sup.2).
[0051] The Ground Plane
[0052] The electrically conductive ground plane 12 may be an
electrically conductive metal layer which may be formed, for
example, on the substrate 10 by any suitable coating technique,
such as a vacuum depositing technique. Metals include aluminum,
zirconium, niobium, tantalum, vanadium, hafnium, titanium, nickel,
stainless steel, chromium, tungsten, molybdenum, and other
conductive substances, and mixtures thereof. The conductive layer
may vary in thickness over substantially wide ranges depending on
the optical transparency and flexibility desired for the
electrophotoconductive member. Accordingly, for a flexible
photoresponsive imaging device, the thickness of the conductive
layer may be at least about 20 Angstroms, or no more than about 750
Angstroms, or at least about 50 Angstroms, or no more than about
200 Angstroms for an optimum combination of electrical
conductivity, flexibility and light transmission.
[0053] Regardless of the technique employed to form the metal
layer, a thin layer of metal oxide forms on the outer surface of
most metals upon exposure to air. Thus, when other layers overlying
the metal layer are characterized as "contiguous" layers, it is
intended that these overlying contiguous layers may, in fact,
contact a thin metal oxide layer that has formed on the outer
surface of the oxidizable metal layer. Generally, for rear erase
exposure, a conductive layer light transparency of at least about
15 percent is desirable. The conductive layer need not be limited
to metals. Other examples of conductive layers may be combinations
of materials such as conductive indium tin oxide as transparent
layer for light having a wavelength between about 4000 Angstroms
and about 9000 Angstroms or a conductive carbon black dispersed in
a polymeric binder as an opaque conductive layer.
[0054] The Hole Blocking Layer
[0055] After deposition of the electrically conductive ground plane
layer, the hole blocking layer 14 may be applied thereto. Electron
blocking layers for positively charged photoreceptors allow holes
from the imaging surface of the photoreceptor to migrate toward the
conductive layer. For negatively charged photoreceptors, any
suitable hole blocking layer capable of forming a barrier to
prevent hole injection from the conductive layer to the opposite
photoconductive layer may be utilized. The hole blocking layer may
include polymers such as polyvinylbutryral, epoxy resins,
polyesters, polysiloxanes, polyamides, polyurethanes and the like,
or may be nitrogen containing siloxanes or nitrogen containing
titanium compounds such as trimethoxysilyl propylene diamine,
hydrolyzed trimethoxysilyl propyl ethylene diamine,
N-beta-(aminoethyl) gamma-amino-propyl trimethoxy silane, isopropyl
4-aminobenzene sulfonyl, di(dodecylbenzene sulfonyl)titanate,
isopropyl di(4-aminobenzoyl)isostearoyl titanate, isopropyl
tri(N-ethylamino-ethylamino)titanate, isopropyl trianthranil
titanate, isopropyl tri(N,N-dimethylethylamino)titanate,
titanium-4-amino benzene sulfonate oxyacetate, titanium
4-aminobenzoate isostearate oxyacetate, [H.sub.2
N(CH.sub.2).sub.4]CH.sub.3Si(OCH.sub.3).sub.2,
(gamma-aminobutyl)methyl diethoxysilane, and
[H.sub.2N(CH.sub.2).sub.3]CH.sub.3Si(OCH.sub.3).sub.2
(gamma-aminopropyl)methyl diethoxysilane, as disclosed in U.S. Pat.
Nos. 4,338,387, 4,286,033 and 4,291,110.
[0056] General embodiments of the undercoat layer may comprise a
metal oxide and a resin binder. The metal oxides that can be used
with the embodiments herein include, but are not limited to,
titanium oxide, zinc oxide, tin oxide, aluminum oxide, silicon
oxide, zirconium oxide, indium oxide, molybdenum oxide, and
mixtures thereof. Undercoat layer binder materials may include, for
example, polyesters, MOR-ESTER 49,000 from Morton International
Inc., VITEL PE-100, VITEL PE-200, VITEL PE-200D, and VITEL PE-222
from Goodyear Tire and Rubber Co., polyarylates such as ARDEL from
AMOCO Production Products, polysulfone from AMOCO Production
Products, polyurethanes, and the like.
[0057] The hole blocking layer should be continuous and have a
thickness of less than about 0.5 micrometer because greater
thicknesses may lead to undesirably high residual voltage. A hole
blocking layer of between about 0.005 micrometer and about 0.3
micrometer is used because charge neutralization after the exposure
step is facilitated and optimum electrical performance is achieved.
A thickness of between about 0.03 micrometer and about 0.06
micrometer is used for hole blocking layers for optimum electrical
behavior. The hole blocking layers that contain metal oxides such
as zinc oxide, titanium oxide, or tin oxide, may be thicker, for
example, having a thickness up to about 25 micrometers. The
blocking layer may be applied by any suitable conventional
technique such as spraying, dip coating, draw bar coating, gravure
coating, silk screening, air knife coating, reverse roll coating,
vacuum deposition, chemical treatment and the like. For convenience
in obtaining thin layers, the blocking layer is applied in the form
of a dilute solution, with the solvent being removed after
deposition of the coating by conventional techniques such as by
vacuum, heating and the like. Generally, a weight ratio of hole
blocking layer material and solvent of between about 0.05:100 to
about 0.5:100 is satisfactory for spray coating.
[0058] The Charge Generation Layer
[0059] The charge generation layer 18 may thereafter be applied to
the undercoat layer 14. Any suitable charge generation binder
including a charge generating/ photoconductive material, which may
be in the form of particles and dispersed in a film forming binder,
such as an inactive resin, may be utilized. Examples of charge
generating materials include, for example, inorganic
photoconductive materials such as amorphous selenium, trigonal
selenium, and selenium alloys selected from the group consisting of
selenium-tellurium, selenium-tellurium-arsenic, selenium arsenide
and mixtures thereof, and organic photoconductive materials
including various phthalocyanine pigments such as the X-form of
metal free phthalocyanine, metal phthalocyanines such as vanadyl
phthalocyanine and copper phthalocyanine, hydroxy gallium
phthalocyanines, chlorogallium phthalocyanines, titanyl
phthalocyanines, quinacridones, dibromo anthanthrone pigments,
benzimidazole perylene, substituted 2,4-diamino-triazines,
polynuclear aromatic quinones, enzimidazole perylene, and the like,
and mixtures thereof, dispersed in a film forming polymeric binder.
Selenium, selenium alloy, benzimidazole perylene, and the like and
mixtures thereof may be formed as a continuous, homogeneous charge
generation layer. Benzimidazole perylene compositions are well
known and described, for example, in U.S. Pat. No. 4,587,189, the
entire disclosure thereof being incorporated herein by reference.
Multi-charge generation layer compositions may be used where a
photoconductive layer enhances or reduces the properties of the
charge generation layer. Other suitable charge generating materials
known in the art may also be utilized, if desired. The charge
generating materials selected should be sensitive to activating
radiation having a wavelength between about 400 and about 900 nm
during the imagewise radiation exposure step in an
electrophotographic imaging process to form an electrostatic latent
image. For example, hydroxygallium phthalocyanine absorbs light of
a wavelength of from about 370 to about 950 nanometers, as
disclosed, for example, in U.S. Pat. No. 5,756,245.
[0060] Any suitable inactive resin materials may be employed as a
binder in the charge generation layer 18, including those
described, for example, in U.S. Pat. No. 3,121,006, the entire
disclosure thereof being incorporated herein by reference. Organic
resinous binders include thermoplastic and thermosetting resins
such as one or more of polycarbonates, polyesters, polyamides,
polyurethanes, polystyrenes, polyarylethers, polyarylsulfones,
polybutadienes, polysulfones, polyethersulfones, polyethylenes,
polypropylenes, polyimides, polymethylpentenes, polyphenylene
sulfides, polyvinyl butyral, polyvinyl acetate, polysiloxanes,
polyacrylates, polyvinyl acetals, polyamides, polyimides, amino
resins, phenylene oxide resins, terephthalic acid resins, epoxy
resins, phenolic resins, polystyrene and acrylonitrile copolymers,
polyvinylchloride, vinylchloride and vinyl acetate copolymers,
acrylate copolymers, alkyd resins, cellulosic film formers,
poly(amideimide), styrene-butadiene copolymers,
vinylidenechloride/vinylchloride copolymers,
vinylacetate/vinylidene chloride copolymers, styrene-alkyd resins,
and the like. Another film-forming polymer binder is PCZ-400
(poly(4,4'-dihydroxy-diphenyl-1-1-cyclohexane) which has a
viscosity-molecular weight of 40,000 and is available from
Mitsubishi Gas Chemical Corporation (Tokyo, Japan).
[0061] The charge generating material can be present in the
resinous binder composition in various amounts. Generally, at least
about 5 percent by volume, or no more than about 90 percent by
volume of the charge generating material is dispersed in at least
about 95 percent by volume, or no more than about 10 percent by
volume of the resinous binder, and more specifically at least about
20 percent, or no more than about 60 percent by volume of the
charge generating material is dispersed in at least about 80
percent by volume, or no more than about 40 percent by volume of
the resinous binder composition.
[0062] In specific embodiments, the charge generation layer 18 may
have a thickness of at least about 0.1 .mu.m, or no more than about
2 .mu.m, or of at least about 0.2 .mu.m, or no more than about 1
.mu.m. These embodiments may be comprised of chlorogallium
phthalocyanine or hydroxygallium phthalocyanine or mixtures
thereof. The charge generation layer 18 containing the charge
generating material and the resinous binder material generally
ranges in thickness of at least about 0.1 .mu.m, or no more than
about 5 .mu.m, for example, from about 0.2 .mu.m to about 3 .mu.m
when dry. The charge generation layer thickness is generally
related to binder content. Higher binder content compositions
generally employ thicker layers for charge generation,
[0063] The Charge Transport Layer
[0064] In a drum photoreceptor, the charge transport layer
comprises a single layer of the same composition. As such, the
charge transport layer will be discussed specifically in terms of a
single layer 20, but the details will be also applicable to an
embodiment having dual charge transport layers. The charge
transport layer 20 is thereafter applied over the charge generation
layer 18 and may include any suitable transparent organic polymer
or non-polymeric material capable of supporting the injection of
photogenerated holes or electrons from the charge generation layer
18 and capable of allowing the transport of these holes/electrons
through the charge transport layer to selectively discharge the
surface charge on the imaging member surface. In one embodiment,
the charge transport layer 20 not only serves to transport holes,
but also protects the charge generation layer 18 from abrasion or
chemical attack and may therefore extend the service life of the
imaging member. The charge transport layer 20 can be a
substantially non-photoconductive material, but one which supports
the injection of photogenerated holes from the charge generation
layer 18.
[0065] The layer 20 is normally transparent in a wavelength region
in which the electrophotographic imaging member is to be used when
exposure is affected there to ensure that most of the incident
radiation is utilized by the underlying charge generation layer 18.
The charge transport layer should exhibit excellent optical
transparency with negligible light absorption and no charge
generation when exposed to a wavelength of light useful in
xerography, e.g., 400 to 900 nanometers. In the case when the
photoreceptor is prepared with the use of a transparent substrate
10 and also a transparent or partially transparent conductive layer
12, image wise exposure or erase may be accomplished through the
substrate 10 with all light passing through the back side of the
substrate. In this case, the materials of the layer 20 need not
transmit light in the wavelength region of use if the charge
generation layer 18 is sandwiched between the substrate and the
charge transport layer 20. The charge transport layer 20 in
conjunction with the charge generation layer 18 is an insulator to
the extent that an electrostatic charge placed on the charge
transport layer is not conducted in the absence of illumination.
The charge transport layer 20 should trap minimal charges as the
charge passes through it during the discharging process.
[0066] The charge transport layer 20 may include any suitable
charge transport component or activating compound useful as an
additive dissolved or molecularly dispersed in an electrically
inactive polymeric material, such as a polycarbonate binder, to
form a solid solution and thereby making this material electrically
active. "Dissolved" refers, for example, to forming a solution in
which the small molecule is dissolved in the polymer to form a
homogeneous phase; and molecularly dispersed in embodiments refers,
for example, to charge transporting molecules dispersed in the
polymer, the small molecules being dispersed in the polymer on a
molecular scale. The charge transport component may be added to a
film forming polymeric material which is otherwise incapable of
supporting the injection of photogenerated holes from the charge
generation material and incapable of allowing the transport of
these holes through. This addition converts the electrically
inactive polymeric material to a material capable of supporting the
injection of photogenerated holes from the charge generation layer
18 and capable of allowing the transport of these holes through the
charge transport layer 20 in order to discharge the surface charge
on the charge transport layer. The high mobility charge transport
component may comprise small molecules of an organic compound which
cooperate to transport charge between molecules and ultimately to
the surface of the charge transport layer. For example, but not
limited to, N,N'-diphenyl-N,N-bis(3-methyl
phenyl)-1,1'-biphenyl-4,4'-diamine (TPD), other arylamines like
triphenyl amine, N,N,N',N'-tetra-p-tolyl-1,1'-biphenyl-4,4'-diamine
(TM-TPD), and the like.
[0067] A number of charge transport compounds can be included in
the charge transport layer, which layer generally is of a thickness
of from about 5 to about 75 micrometers, and more specifically, of
a thickness of from about 15 to about 40 micrometers. Examples of
charge transport components are aryl amines of the following
formulas/structures:
##STR00004##
wherein X is a suitable hydrocarbon like alkyl, alkoxy, aryl, and
derivatives thereof; a halogen, or mixtures thereof, and especially
those substituents selected from the group consisting of Cl and
CH.sub.3; and molecules of the following formulas
##STR00005##
wherein X, V and Z are independently alkyl, alkoxy, aryl, a
halogen, or mixtures thereof, and wherein at least one of Y and Z
are present.
[0068] Alkyl and alkoxy contain, for example, from 1 to about 25
carbon atoms, and more specifically, from 1 to about 12 carbon
atoms, such as methyl, ethyl, propyl, butyl, pentyl, and the
corresponding alkoxides. Aryl can contain from 6 to about 36 carbon
atoms, such as phenyl, and the like. Halogen includes chloride,
bromide, iodide, and fluoride. Substituted alkyls, alkoxys, and
aryls can also be selected in embodiments.
[0069] Examples of specific aryl amines that can be selected for
the charge transport layer include
N,N'-diphenyl-N,N'-bis(alkylphenyl)-1,1-biphenyl-4,4'-diamine
wherein alkyl is selected from the group consisting of methyl,
ethyl, propyl, butyl, hexyl, and the like;
N,N'-diphenyl-N,N'-bis(halophenyl)-1,1'-biphenyl-4,4'-diamine
wherein the halo substituent is a chloro substituent;
N,N'-bis(4-butylphenyl)-N,N'-di-p-tolyl-[p-terphenyl]-4,4''-diamine,
N,N'-bis(4-butylphenyl)-N,N'-di-m-tolyl-[p-terphenyl]-4,4''-diamine,
N,N'-bis(4-butylphenyl)-N,N'-di-o-tolyl-[p-terphenyl]-4,4''-diamine,
N,N'-bis(4-butylphenyl)-N,N'-bis-(4-isopropylphenyl)-[p-terphenyl]-4,4''--
diamine,
N,N'-bis(4-butylphenyl)-N,N'-bis-(2-ethyl-6-methylphenyl)-[p-terp-
henyl]-4,4''-diamine,
N,N'-bis(4-butylphenyl)-N,N'-bis-(2,5-dimethylphenyl)-{p-terphenyl]-4,4'--
diamine,
N,N'-diphenyl-N,N'-bis(3-chlorophenyl)-[p-terphenyl]-4,4''-diamin-
e, and the like. Other known charge transport layer molecules may
be selected in embodiments, reference for example, U.S. Pat. Nos.
4,921,773 and 4,464,450, the disclosures of which are totally
incorporated herein by reference.
[0070] Examples of the binder materials selected for the charge
transport layers include components, such as those described in
U.S. Pat. 3,121,006, the disclosure of which is totally
incorporated herein by reference. Specific examples of polymer
binder materials include polycarbonates, polyarylates, acrylate
polymers, vinyl polymers, cellulose polymers, polyesters,
polysiloxanes, polyamides, polyurethanes, poly(cyclo olefins), and
epoxies, and random or alternating copolymers thereof. In
embodiments, the charge transport layer, such as a hole transport
layer, may have a thickness of at least about 10 .mu.m, or no more
than about 40 .mu.m.
[0071] Examples of components or materials optionally incorporated
into the charge transport layers or at least one charge transport
layer to, for example, enable improved lateral charge migration
(LCM) resistance include hindered phenolic antioxidants such as
tetrakis methylene(3,5-di-tert-butyl-4-hydroxy hydrocinnamate)
methane (IRGANOX.RTM. 1010, available from Ciba Specialty
Chemical), butylated hydroxytoluene (BHT), and other hindered
phenolic antioxidants including SUMILIZER.TM. BHT-R, MDP-S, BBM-S,
WX-R, NW, BP-76, BP-101, GA-80, GM and GS (available from Sumitomo
Chemical Co., Ltd.), IRGANOX.RTM. 1035, 1076, 1098, 1135, 1141,
1222, 1330, 1425WL, 1520L, 245, 259, 3114, 3790, 5057 and 565
(available from Ciba Specialties Chemicals), and ADEKA STAB.TM.
AO-20, AO-30, AO-40, AO-50, AO-60, AO-70, AO-80 and AO-330
(available from Asahi Denka Co., Ltd.); hindered amine antioxidants
such as SANOL.TM. LS-2626, LS-765, LS-770 and LS-744 (available
from SANKYO CO., Ltd.), TINUVIN.RTM. 144 and 622LD (available from
Ciba Specialties Chemicals), MARK.TM. LA57, LA67, LA62, LA68 and
LA63 (available from Asahi Denka Co., Ltd.), and SUMILIZER.RTM. TPS
(available from Sumitomo Chemical Co., Ltd.); thioether
antioxidants such as SUMILIZER.RTM. TP-D (available from Sumitomo
Chemical Co., Ltd); phosphite antioxidants such as MARK.TM. 2112,
PEP-8, PEP-24G, PEP-36, 329K and HP-10 (available from Asahi Denka
Co., Ltd.); other molecules such as
bis(4-diethylamino-2-methylphenyl)phenylmethane (BDETPM),
bis-[2-methyl-4-(N-2-hydroxyethyl-N-ethyl-aminophenyl)}-phenylmethane
(DHTPM), and the like. The weight percent of the antioxidant in at
least one of the charge transport layer is from about 0 to about
20, from about 1 to about 10, or from about 3 to about 8 weight
percent.
[0072] The charge transport layer should be an insulator to the
extent that the electrostatic charge placed on the hole transport
layer is not conducted in the absence of illumination at a rate
sufficient to prevent formation and retention of an electrostatic
latent image thereon. The charge transport layer is substantially
nonabsorbing to visible light or radiation in the region of
intended use, but is electrically "active" in that it allows the
injection of photogenerated holes from the photoconductive layer,
that is the charge generation layer, and allows these holes to be
transported through itself to selectively discharge a surface
charge on the surface of the active layer.
[0073] In addition, in the present embodiments using a belt
configuration, the charge transport layer may consist of a single
pass charge transport layer or a dual pass charge transport layer
(or dual layer charge transport layer) with the same or different
transport molecule ratios. In these embodiments, the dual layer
charge transport layer has a total thickness of from about 10 .mu.m
to about 40 .mu.m. In other embodiments, each layer of the dual
layer charge transport layer may have an individual thickness of
from 2 .mu.m to about 20 .mu.m. Moreover, the charge transport
layer may be configured such that it is used as a top layer of the
photoreceptor to inhibit crystallization at the interface of the
charge transport layer and the overcoat layer. In another
embodiment, the charge transport layer may be configured such that
it is used as a first pass charge transport layer to inhibit
microcrystallization occurring at the interface between the first
pass and second pass layers.
[0074] Any suitable and conventional technique may be utilized to
form and thereafter apply the charge transport layer mixture to the
supporting substrate layer. The charge transport layer may be
formed in a single coating step or in multiple coating steps. Dip
coating, ring coating, spray, gravure or any other drum coating
methods may be used.
[0075] Drying of the deposited coating may be effected by any
suitable conventional technique such as oven drying, infra red
radiation drying, air drying and the like. The thickness of the
charge transport layer after drying is from about 10 .mu.m to about
40 .mu.m or from about 12 .mu.m to about 36 .mu.m for optimum
photoelectrical and mechanical results. In another embodiment the
thickness is from about 14 .mu.m to about 36 .mu.m.
[0076] The Adhesive Layer
[0077] An optional separate adhesive interface layer may be
provided in certain configurations, such as for example, in
flexible web configurations. In the embodiment illustrated in FIG.
1, the interface layer would be situated between the blocking layer
14 and the charge generation layer 18. The interface layer may
include a copolyester resin. Exemplary polyester resins which may
be utilized for the interface layer include
polyarylatepolyvinylbutyrals, such as ARDEL POLYARYLATE (U-100)
commercially available from Toyota Hsutsu Inc., VITEL PE-100, VITEL
PE-200, VITEL PE-200D, and VITEL PE-222, all from Bostik, 49,000
polyester from Rohm Hass, polyvinyl butyral, and the like. The
adhesive interface layer may be applied directly to the hole
blocking layer 14. Thus, the adhesive interface layer in
embodiments is in direct contiguous contact with both the
underlying hole blocking layer 14 and the overlying charge
generator layer 18 to enhance adhesion bonding to provide linkage.
In yet other embodiments, the adhesive interface layer is entirely
omitted.
[0078] Any suitable solvent or solvent mixtures may be employed to
form a coating solution of the polyester for the adhesive interface
layer. Solvents may include tetrahydrofuran, toluene,
monochlorbenzene, methylene chloride, cyclohexanone, and the like,
and mixtures thereof. Any other suitable and conventional technique
may be used to mix and thereafter apply the adhesive layer coating
mixture to the hole blocking layer. Application techniques may
include spraying, dip coating, roll coating, wire wound rod
coating, and the like. Drying of the deposited wet coating may be
effected by any suitable conventional process, such as oven drying,
infra red radiation drying, air drying, and the like.
[0079] The adhesive interface layer may have a thickness of at
least about 0.01 micrometers, or no more than about 900 micrometers
after drying. In embodiments, the dried thickness is from about
0.03 micrometers to about 1 micrometer.
[0080] The Ground Strip
[0081] The ground strip may comprise a film forming polymer binder
and electrically conductive particles. Any suitable electrically
conductive particles may be used in the electrically conductive
ground strip layer 19. The ground strip 19 may comprise materials
which include those enumerated in U.S. Pat. No. 4,664,995.
Electrically conductive particles include carbon black, graphite,
copper, silver, gold, nickel, tantalum, chromium, zirconium,
vanadium, niobium, indium tin oxide and the like. The electrically
conductive particles may have any suitable shape. Shapes may
include irregular, granular, spherical, elliptical, cubic, flake,
filament, and the like. The electrically conductive particles
should have a particle size less than the thickness of the
electrically conductive ground strip layer to avoid an electrically
conductive ground strip layer having an excessively irregular outer
surface. An average particle size of less than about 10 micrometers
generally avoids excessive protrusion of the electrically
conductive particles at the outer surface of the dried ground strip
layer and ensures relatively uniform dispersion of the particles
throughout the matrix of the dried ground strip layer. The
concentration of the conductive particles to be used in the ground
strip depends on factors such as the conductivity of the specific
conductive particles utilized.
[0082] The ground strip layer may have a thickness of at least
about 7 micrometers, or no more than about 42 micrometers, or of at
least about 14 micrometers, or no more than about 27
micrometers.
[0083] The Anti-Curl Back Coating Layer
[0084] The anti-curl back coating 1 may comprise organic polymers
or inorganic polymers that are electrically insulating or slightly
semi-conductive. The anti-curl back coating provides flatness
and/or abrasion resistance.
[0085] Anti-curl back coating 1 may be formed at the back side of
the substrate 2, opposite to the imaging layers. The anti-curl back
coating may comprise a film forming resin binder and an adhesion
promoter additive. The resin binder may be the same resins as the
resin binders of the charge transport layer discussed above.
Examples of film forming resins include polyacrylate, polystyrene,
bisphenol polycarbonate, poly(4,4'-isopropylidene diphenyl
carbonate), 4,4'-cyclohexylidene diphenyl polycarbonate, and the
like. Adhesion promoters used as additives include 49,000 (du
Pont), Vitel PE-100, Vitel PE-200, Vitel PE-307 (Goodyear), and the
like. Usually from about 1 to about 15 weight percent adhesion
promoter is selected for film forming resin addition. The thickness
of the anti-curl back coating is at least about 3 micrometers, or
no more than about 35 micrometers, or about 14 micrometers.
[0086] Various exemplary embodiments encompassed herein include a
method of imaging which includes generating an electrostatic latent
image on an imaging member, developing a latent image, and
transferring the developed electrostatic image to a suitable
substrate.
[0087] While the description above refers to particular
embodiments, it will be understood that many modifications may be
made without departing from the spirit thereof. The accompanying
claims are intended to cover such modifications as would fall
within the true scope and spirit of embodiments herein.
[0088] The presently disclosed embodiments are, therefore, to be
considered in all respects as illustrative and not restrictive, the
scope of embodiments being indicated by the appended claims rather
than the foregoing description. All changes that come within the
meaning of and range of equivalency of the claims are intended to
be embraced therein.
EXAMPLES
[0089] The example set forth herein below and is illustrative of
different compositions and conditions that can be used in
practicing the present embodiments. All proportions are by weight
unless otherwise indicated. It will be apparent, however, that the
embodiments can be practiced with many types of compositions and
can have many different uses in accordance with the disclosure
above and as pointed out hereinafter.
Example 1
[0090] Fabrication of Delivery Members
[0091] A crosslinkable polydimethylsiloxane (PDMS) base and curing
agent (Sylgard 184, Dow Corning) were mixed together in a 10:1
ratio by mass. The components were stirred together. To this
mixture was added paraffin oil in a ratio of 2:1 PDMS to paraffin
oil. The mixture was stirred together until a viscous mixture was
obtained. The mixture was injected into a cylindrical mold, and
degassed for one hour. The remaining mold was assembled and the
PDMS:paraffin mixture was cured in a forced air lab oven at
60.degree. C. for three hours. The delivery roller was extracted
from the mold and incorporated into a CRU for print testing.
Example 2
[0092] Fabrication of Photoreceptor
[0093] The photoreceptor was fabricated in the following manner. A
coating solution for an undercoat layer comprising 100 parts of a
ziconium compound (trade name: Orgatics ZC540), 10 parts of a
silane compound (trade name: A110, manufactured by Nippon Unicar
Co., Ltd), 400 parts of isopropanol solution and 200 parts of
butanol was prepared. The coating solution was applied onto a 30-mm
cylindrical aluminum (Al) substrate subjected to honing treatment
by dip coating, and dried by heating at 150.degree. C. for 10
minutes to form an undercoat layer having a film thickness of 0.1
micrometer.
[0094] A 0.5 micron thick charge generating layer was subsequently
dip coated on top of the undercoat layer from a dispersion of Type
V hydroxygallium phthalocyanine (12 parts), alkylhydroxy gallium
phthalocyanine (3 parts), and a vinyl chloride/vinyl acetate
copolymer, VMCH (Mn=27,000, about 86 weight percent of vinyl
chloride, about 13 weight percent of vinyl acetate and about 1
weight percent of maleic acid) available from Dow Chemical (10
parts), in 475 parts of n-butylacetate,
[0095] Subsequently, a 20 .mu.m thick charge transport layer (CTL)
was dip coated on top of the charge generating layer from a
solution of
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine
(82.3 parts), 2.1 parts of 2,6-di-tert-butyl-4-methylphenol (BHT)
from Aldrich and a polycarbonate, PCZ-400
[poly(4,4'-dihydroxy-diphenyl-1-1-cyclohexane), M.sub.w=40,000]
available from Mitsubishi Gas Chemical Company, Ltd. (123.5 parts)
in a mixture of 546 parts of tetrahydrofuran (THF) and 234 parts of
monochlorobenzene. The CTL was dried at 115.degree. C. for 60
minutes.
[0096] An overcoat coating solution was prepared from a mixture of
N,N,N',N'-tetrakis-[(4-hydroxymethyl)phenyl]-biphenyl-4,4'-diamine
(3.22 g parts),
N,N'-diphenyl-N,N'-bis-(3-hydroxyphenyl)-biphenyl-4,4'-diamine
(7.98 g parts), melamine-formaldehyde resin (2.10 parts), a
silicone leveling agent (0.5 parts), an anti-oxidant (0.4 part),
and an acid catalyst (0.65 part) in a solvent of
1-methoxy-2-propanol (40.3 parts). The mixture was mixed on a
rolling wave rotator for 10 min and then heated at 50.degree. C.
for 65 min until a homogenous solution resulted, then cooled to
room temperature. After filtering with a 1-.mu.m PTFE filter, the
solution was applied onto the photoreceptor surface and more
specifically onto the charge transport layer using cup coating
technique, followed by thermal curing at 155.degree. C. for 40
minutes to form an overcoat layer having a film thickness of 6
.mu.m.
Example 3
[0097] Fabrication of Image Forming Apparatus
[0098] Xerox Workcentre 7435 CRU was modified by replacing the BCR
foam cleaner with the delivery member as fabricated in Example 1,
and placing an overcoated photoreceptor as fabricated in Example 2.
The good conformal contact between the delivery roll and BCR was
examined to ensure smooth rotation. In this manner, the delivery
roller applied first a thin layer of paraffin onto the BCR roll,
which in returns applied the paraffin onto the surface of
photoreceptor as it rotated.
[0099] Evaluation and Testing Results
[0100] The imaging apparatus as assembled in Example 3 was placed
in Xerox Workcentre 7435 printer. Print test was conducted in a
stressful environment (A-zone: 28.degree. C., 85% RH) to evaluate
image quality, specifically halftone and deletion. For comparison,
as shown in FIG. 5, the delivery roller was adjusted to cover two
thirds the width of the BCR roller, so that the paraffin was
applied onto two thirds of the photoreceptor 54 and the non-applied
surface 52 was used as control. The image quality of the print was
compared after 25,000 prints were completed. As shown in FIG. 6,
good image (i.e. no deletion) was observed for the printed area
where paraffin was applied, as compared to the poor image observed
in the control section.
[0101] The applied paraffin also helped reduced the damage of the
blade cleaner. From optical observation, the portion of the
cleaning blade that contacted the control portion 52 of the
photoreceptor (without paraffin applied) exhibited partial damage
on the leading edge. in comparison, the test portion of the
photoreceptor 54 (with paraffin applied) exhibited much less
damage.
[0102] The testing results illustrated herein demonstrate that the
delivery roll can deliver a layer of paraffin onto photoreceptor
through BCR roller. The applied paraffin as functional material
effectively improves the image quality for overcoated
photoreceptor, and helps improve interaction between the
photoreceptor and cleaning blade. In practical applications, the
delivery roll should cover the full length of the BCR roller, so
that the paraffin functional material can be applied onto the full
area of the photoreceptor.
[0103] In summary, the present embodiments describe a method and
apparatus for delivering a continuous supply of hydrophobic
functional material that represents a breakthrough approach toward
the goal of a long life photoreceptors by substantially reducing
torque and image defects. The method and apparatus uses only a
delivery member fabricated with the functional materials, thus
eliminating the need for a separate supply container. The delivery
method and apparatus is compact in size and can be implemented in a
small CRU, such as for example, a CRU having 30 mm drum diameter.
In addition, the present embodiments provide a way to deliver the
ultra-thin layer of hydrophobic material by the delivery member
onto the photoreceptor by using the BCR as an intermediate donor
roller.
[0104] All the patents and applications referred to herein are
hereby specifically, and totally incorporated herein by reference
in their entirety in the instant specification.
[0105] It will be appreciated that several of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims. Unless specifically recited in a claim, steps or components
of claims should not be implied or imported from the specification
or any other, claims as to any particular order, number, position,
size, shape, angle, color, or material,
* * * * *